Group III-based ceramic materials have a variety of uses. Examples of Group III materials include (1) alumina (Al2O3), (2) ferroelectric lanthanide-containing materials, such as bismuth lanthanum titanate (BLT), and (3) gallium compounds.
In particular, of concern are the synthesis, processing, and fabrication of the Group III-based materials into thin film is, coatings, thick films, and bulk ceramic materials for, e.g., electronic devices and, in the case of gallium, for oral delivery (gallium has been shown to be a therapeutic agent for certain cancers and for protecting bone).
Metal-organic decomposition (MOD) deposition processes are known for a number of ceramic materials. The MOD process typically involves the synthesis of thin film ceramics from metal organic acid salts (mostly aliphatic acids such as neo-decanoic acid or 2-ethylhexanoic acid). The MOD process is described in, for example, (1) U.S. Pat. No. 5,721,009, “Controlled Carbon Content MOD Precursor Materials Using Organic Acid Anhydride”, issued to Thomas K. Dougherty et al on Feb. 24, 1998; (2) J. V. Mantese et al, “Metalorganic Deposition (MOD): A Nonvacuum, Spin-on, Liquid-Based, Thin Film Method”, MRS Bulletin, pp. 48-53 (October 1989); (3) WO 93/12538, “Process for Fabricating Layered Superlattice Materials”, filed in the names of Carlos A. Paz de Araujo et al, published on 24 Jun. 1993; (4) U.S. Pat. No. 5,434,102 (issued on Jul. 18, 1995) and U.S. Pat. No. 5,439,845 (issued on Aug. 8, 1995), to Hitoshi Watanabe et al and both entitled “Process for Fabricating Layered Superlattice Materials and Making Electronic Devices Including Same”; and (5) G. M. Vest et al, “Synthesis of Metallo-Organic Compounds for MOD Powders and Films”, Materials Research Society Symposium Proceedings, Vol. 60, pp. 35-42 (1986).
The present inventors and associates have continued their work in this area, culminating in (1) U.S. Pat. No. 6,054,600, “Non-Toxic Solvent Soluble Group IV and V Metal Acid Salt Complexes Using Polyether Acid Anhydrides”, issued to T. Kirk Dougherty et al on Apr. 25, 2000; (2) U.S. Pat. No. 6,303,804, “Environmentally Benign Bismuth-Containing Spin-on Precursor Materials”, issued to T. Kirk Dougherty et al on Oct. 16, 2001; (3) U.S. Pat. No. 6,316,651, “Environmentally Benign Group II and Group IV or V Spin-on Precursor Materials”, issued to T. Kirk Dougherty et al on Nov. 13, 2001, and (4) application Ser. No. 10/771,066, filed Feb. 2, 2004. The contents of these patents and patent application are incorporated herein by reference.
Similar alumina-forming polyether acid materials have been described by Barron in, for example, U.S. Pat. No. 6,322,890, and Chem. Mater., Vol. 9, pp. 2418-2433 (1997) useful as ceramic binders and fillers and as polymerization catalysts. In this case, the materials are formed by a high temperature reaction of the free acids with alumina minerals that takes a long time. Thus, the materials of Barron do not appear to be as easy to make, as soluble or as easy to characterize and process as the alumina materials as described herein.
Lanthanum-doped bismuth titanate (BLT) is a newer ferroelectric material that has recently been developed. BLT prior art includes Park et al, Nature, Vol. 401, pp. 682-684 (October 1999); Bao et al, J. Appl. Phys., Vol. 93(1), pp. 497-503 (1 Jan. 2003); and Kojima et al, J. Appl. Phys., Vol. 93(3), pp. 1707-1712 (1 Feb. 2003).
Of note is a single reference for the yttria precursors of the polyether acids, namely, Apblett et al in Phosphorous, Sulfur and Silicon, Vol. 93-94, pp. 481-482 (1994).
Finally, gallium maltolate is being investigated as a water-stable and soluble oral delivery mechanism for gallium. The use of gallium organic salts for therapeutic uses is desirable if these materials can be made easier to synthesize and characterize than presently. Further, it would be desirable to tailor the gallium compounds as to bioavailability.
Thus, there remains a need for a soluble Group III containing precursor which is compatible and soluble in non-toxic and environmentally benign solvents (including water), has unlimited stability and shelf life, and provides high quality Group III-containing films and materials.